There have been known heretofore in the prior art apparatus for making fabricless surface coverings. Commonly, such apparatus have included some form of hopper means for depositing particles of synthetic resin onto an endless conveyer which then carries a synthetic resin through an oven where it is fused, then between a pair of embossing rolls, and finally passed a cooling means. One such apparatus is described and illustrated in U.S. Pat. No. 3,192,294 which issued June 29, 1965. A disadvantage, however, of such prior art forms of apparatus is that they possess very little capability for adjustment insofar as concerns obtaining and maintaining the optimum heating temperature gradient required for manufacturing a given type of fabricless surface covering. That is, although the heating temperature gradient in the oven assembly normally may be preset at different levels for manufacturing different types of fabricless surface coverings, only limited means are provided for compensating either manually or automatically for deviation from the preset temperature profile occurring during the manufacturing operation.
However, in order to ensure the quality of the fabricless surface covering being manufactured, it is important that the heating of the synthetic resin from which the surface covering is made be accomplished in accordance with a preestablished temperature profile. In the event the synthetic resin is heated in accordance with a temperature profile which is somewhat lower or somewhat higher than the desired temperature profile, the resulting surface covering produced under these conditions is very likely to be defective and, therefore, not be usable for its intended purpose. For instance, if the synthetic resin is not heated in accordance with the proper temperature profile across the length of an assembly as it passes through the oven assembly, the synthetic resin may be insufficiently heated such that it does not fully fuse but rather remains in a tacky state. On the other hand, if the synthetic resin is heated excessively, the plasticizer may be driven out of the resin such that the latter is then incapable of fusing.
It is also important in order to attain satisfactory results from the fusing operation that the heating of the synthetic resin be accomplished in accordance with a progressively rising temperature profile. That is, the synthetic resin should be heated to a higher and higher temperature progressively rather than in accordance with a series of erratic higher and/or lower temperature changes. To this end, it is important that the temperature gradients in adjacent areas of the oven assembly bear a predetermined relationship to each other. The prior art apparatus which have been known heretofore have been limited, however, insofar as concerns their capability to ensure the existance of such a progressively rising temperature gradient.
Finally, it is important that excess heat buildup be avoided in the oven assembly. Such heat buildup may occur, for example, as a result of prolonged usage of the apparatus. Another possible cause of heat buildup in the oven assembly is ineffective operation of the exhaust system which is normally to be found associated with the oven assembly as a means of eliminating the fumes, etc. from the gas heaters commonly employed in such oven assemblies. It is, therefore, desirable that the apparatus be provided with means for regulating the exhaust to enable a greater degree of heat to be exhausted on occasions when excess heat buildup begins to occur.
Accordingly, it is an object of the present invention to provide a novel and improved apparatus for making fabricless surface coverings which embodies an oven assembly having a temperature control system associated therewith for setting and maintaining a predesired temperature profile across the several successive heating zones within the oven assembly during the manufacturing operation.
It is also an object of the present invention to provide such an apparatus for making fabricless surface covering wherein the oven assembly includes a plurality of heaters which are automatically adjustable to compensate for deviations sensed in the temperature within a given zone profile within the oven assembly from that preestablished for that zone of the oven assembly.
Another object of the present invention is to provide such an apparatus for making fabricless surface coverings which by virtue of ensuring control over the temperature profile across the several successive heating zones during the heating operation enables the consistent production of a quality fabricless surface covering.